Manufacture of cemented armor-plates and other articles of steel or alloys of steel.



'UNITED snares PATENT or tion.

FEDERICO GIOLI'ITI, OF ROME, ITALY, ASSIGNOR TO SOCIETA ANONIMA. ITALIANA GIO. ANSALDO ARMSTRONG 8a 0., OF GENOA, ITALY.

MANUFACTURE OF CEMTNTEI) ARMOR-PLATES AND OTHER ARTICLES OF STEEL 0R ALLOYS OF STEEL.

N 0 Drawing.

Specification of Letters Patent.

Application filed August 31, 1908.

Patented May 9, 1911. Serial No. 451,051.

To all whom it may concern:

Be it known that I, FEDERIGO Gionrrrr, a subject of the King of Italy, and residing at No. 35 Via Palest-ro, Rome, Italy, professor of chemistry, have invented certain new and useful Improvements in the Manufacture of Cemented Armor-Plates and other Articles of Steel or Alloys of Steel, of which the following is a. specification.

This invention consists in improvements in the manufacture of cemented armor plates of steel and alloys of steel (hereinafter included in the term .steel) for ships and other uses.

The methods employed hitherto for introducing carbon into a mass of steel or iron by di'lt'usion Without melting the metal (which method is designated by the generic name of cementation) may be divided into two distinct types.

The first type consists in heating the iron or steel article to be cemented, to a. suitable temperature (usually in the neighborhood of the melting point of cast iron) and in pressing against one or more surfaces of the said article a mixture of solid sub stances (such as various organic substances or cyanids, :ferrocyanids, etc), in the powdered or granular .t'orm containing carbon in the free state or in the state of unstable combination.

The second type consists in heating the steel or iron article to a high temperature, without melting it, in an atmosphere of various carbureted gases such as saturated and non-satin 'atcd gaseous carbids of hydrogen; vapors of volatile carbids of hydrogen, with or without an admixture of nitrogenous substances, etc.

In the methods of the second type (cementation by means of employed hitherto, the influence of temperature on the speed of diffusion and penetration ot the carbon in the mass of solid metal is taken into consideration, and certain limiting temperatures have been determined between which the diffusion takes place most rapidly. Those methods however do not simultaneously take into consideration another very important factor, namely the pressure of the carbureting gas.

Now the improved process forming the subject of the present invention is based on the employment of determined pressures of the carburcting gas relatively to the tom-- pcrat are at which the cementation takes place and to the chemical nature of the gases or vapors employed in the cementation process.

The improved process consists substautially in heating the article to be cemented, in a gaseous ear-bursting medium under a relatively high pressure at a relatively high temperature.

By suitably selecting pressures relatively to the temperature of cen'ieutation and the chemical nature of the gases or vapors employed in the ccmentation process (and also relatively to the nature of the solid carbureting substances which may be employed with the gases and vapors), the duration of the cementation process can be considerably shortened, or a deeper penetration of the carbon can be obtained in the same time.

Generally the speed of the penetration of the carbon into a mass of iron or steel, or what is equivalent thereto, the depth to which the carbon penetrates during a determined length of time into the mas-s, increases considerably with an increase in the pressure oi" the carburet'ing gas, provided that the increase in pressure is accompanied by a suitable variation of the temperature at which the ccmcntation process takes place. This is e'l'l'ccted by raising the temperature when the reaction 01 thedccompositiml of the carlnireting gas (when the gas gives up carbon to the steel) is endothermic, and by lowering'the temperature when the reaction is exothermic. All this applies to cases in which the dccomposition oi. the carlnireting gas or vapor takes place with a dii'ninntion of volume.

In cases in which the decomposition is attended by an increase of volume, all the above relations must be reversed.

In general, a very great advantage will be obtained by ellecting the cemental'ion in an ati'nosphere of earlnibcting gases or vapors under a higher or lower pressure according to the nature of the said gases or vapors, provided that the temperature is varied at the same time in accordance with the above stated rules.

The following example is given with the obyuz', 01' illustrating the manner of p fornzni this invention. It is assumed that ltl i I burized layer, if the temperature or the presit is desiredto cement by means of carbon monoxid a mild steel of approximately the following composition v Carbon 0.1 to 0.2 per cent. Manganese- 0.2 F 0 F Phosphorus m 0.02 0.0a '5 Silicon atraces. Sulfurnflifl traces.

Now the, reaction expressed by. the equa tion 2CO:CO {O according to whichthe carbon monoxid ban give up one halfcf its carbon to the steel, is endothermiciandit is attended by a diminution in the volumeot the gas. Therefore the cementationff will be efiected more quickly by increasing 'the pressure of the gas, provided that inaccord-I, ance with the above statedrule, they-tern;- perature is raised at the same time; ConseL-YE quently, while 'ceme'ntation with carbon men'- oxid at the ordinary pressure, is carried out with advantage at a temperature of from .950 to 1000 degrees C. it the processbe car-. ried out at a pressure of say, over four. at-' mospheres, the temperature must be in; cre sed "to about 11 00- degrees/C. Under these conditions of temperature and pressure it is easy to obtain in less than, 12 hours,

in-a steel of the above specified composition, 'a highly carburet'ed layer having a depth of 8 to 9 millimeters, whereas in operating at the ordinary pressure the depth of the hijg hly carbureted layer which. is obtained during. the same ,peridd of time does-not,

exceed '2 to 3 millimeters. Then by alternately increasing and dim nishing the. pressure and temperatur.ej,=".successive layers may a be produced having a reater or less degree of carburation.

As the intensity of the carburation in creases with the increase of the temperature and pressure; and as the diffusion of the carbon toward the'iiiterior ot the article to be cemented proceeds continuously every time-that the temperature or the pressureis. raised, this will produi ceflon the outside of the article a more strongly. carburized layer which then slowly diifuses toward the inthe lterior and may he followed by a less car- {much shorter period the-steel is much less 7 treatment. Third. By suitably varying theliable to undergo the deterioration of its physical and-mechanical properties which always accompanies much thermal treatment and which must be corrected by subsequent steel articles to; be I V rounded by a coarse powderf'composed of a and 4.0 per cent. of] nine;

eoneva the above stated rule, it-is possible to obtain zones of dlflerent degrees of carburation 1n the different successive layers.

The improved process produces still better results if the steel articles that are subjected to theaction of carbureting gases and vapors under pressure (at a temperature. de-

termined in the mannerabove stated), be

immersed totally or partially in' a mixture charcoal, potassium ferrocyanid, cyanid, etc,

employed separately or mixed together) capable of reacting or not reacting with the carbureting gas or vapor. These solid substances mustbe suitably pressed upon the which is either inherent int-hem, or' arises articles to be cemented b'utso a 'sto allow thegases to pass freely through the inter 'stices of their mass. Theseisubstances, besides exercising their; oarburetingpower from their reactions .withthe, gases, have also the function of facilitating the "transi'nissioiroi heat to the masses pfsteel-i. Thus for instance, in the particular case hereinbefore described, the ccnibination v attains in a given timea maximuinid dpth' when the cemented? are Surf, vegetable eh arcoal harcoal. conr w 11 such a manner as to fill the space mixture of 60 per ce tainedin the cementin v o v e V flies. unoccupied gby thefsteel articles, but so as to allow. th e carhon monoxid under pressure topass with adequate ease through the intersticesof the powder.

. Having thus described my'invcntion what lclaim as new and desire to secure byjLetters Patent is-r' 1 l. The improved process of cementation of armor plates. or,other articles of steel,

which consists in heating the article in a The improved process of cementation i of armor'plates "or other; articles of steel,

which consists -in' heating the steel article in the presence of agranular carboniferous material through whicha current of carbu reting gaseous medium isicai sed tocirculate at atemperat'ure endother'mic' the menting react-ion, and

under a relativelyi'ihigh-.'pressure which is.

higher the greater thegdiminution produced tab is higher the more" by said reactioh' 'in. the volumeotthe gasepressure and the temperature according to one med1.um,'jsaid temperature and "pressure being directly dependent on each other, so that when the temperature is increased the pressure must also be increased, and V100 \"ersa.

The improved process of cementation of armor plates or other articles of steel,

which consists in heating the steel article in a current of gaseous carbureting medium under a pressure exceeding four atmospheres at a temperature of about 1100 degrees centigrade.

4. The improved process 01" eomentation of armor plates or other articles of steel, which consists in heating the steel article G. B. ZAMARDO, G. BIZZARI. 

